Thermochromic Polymer Research Articles

3D Micropatterning With Thermochromic Polymer Microfiber

AbstractAlthough 3D micropattern has received considerable attention due to their remarkable usability, the introduction of specific functions, such as “chromism”, is still a challenge mainly due to the lack of adequate functional materials that can be introduced into 3D printing system. In this study, 3D micropatterns with temperature‐responsive properties are created by elaborately aligned thermochromic polymer microfibers using charge reversal electro‐jet writing (CREW) method with a 3D printer. A reversible color change in response to the temperature change is exhibited in the micropattern, displaying various chromic colors, such as red, blue, and black, at their own thermochromic temperatures. Multiple‐color phases can be sequentially expressed in a single structure by incorporating pigments of different colors with distinguishable color shift ranges. Various patterning methods are proposed for manufacturing diverse patterns and demonstrating applications using combinations of color. In addition to directly increasing temperature, the thermochromic process of micropatterns can be induced by heat generated from external factors using electrical energy. These 3D thermochromic micropatterns using the CREW method can be extended to various fields, including sensors, clothing, and anti‐counterfeiting.

Advancing toward the commercial viability threshold of smart windows utilizing thermochromic polymer blends

Advancing toward the commercial viability threshold of smart windows utilizing thermochromic polymer blends

Thermochromic Polymers in Food Packaging: A Comprehensive Systematic Review and Patent Landscape Analysis

This study addresses the gap in research on the application of thermochromic polymers (TPs) in food packaging and their potential for real-time temperature monitoring, aiding in the assessment of food quality and shelf-life. TPs exhibit a visible color change in response to temperature variations. A comprehensive systematic review (SR) across multiple engineering peer-review databases using predefined terms was conducted. Additionally, international patent databases were investigated using the same predefined terms. Independent experts reviewed the methodology to identify and address potential biases. A total of 288 eligible articles and 922 patents were identified. After a duplicate selection and extraction process according to the inclusion criteria, four related full-text publications were selected from the initial 288 articles, and five relevant patents were selected from the 922 patents. The qualitative review suggests that TPs hold significant promise as food packaging materials due to their unique physical properties. The study concludes that TPs offer valuable properties for the food packaging industry, meriting further investigation to exploit their benefits fully.

Ultra-high Performance Thermochromic Polymers via a Solid-solid Phase Transition Mechanism and Their Applications.

Thermochromic materials are substances that change color in response to temperature variations. Today, sustainability concerns are the main drivers of thermochromic research, with smart, energy-efficient windows being one of the primary applications. While vanadium oxides and leuco dyes are traditionally the main thermochromic materials, hydrogels operating based on change of solvation have risen as some of the most promising materials due to their high optical transparency and good solar modulating abilities. In this work, a distinct mechanism for thermochromism arising from the crystalline solid to amorphous solid polymer transition, with a corresponding transition from an opaque state to a transparent state is disclosed. Both ultra-high optical transparency (Tlum up to 99%) and ultra-high solar modulation (ΔTsolar up to 87%) are observed. The transition temperature is tunable from 11 to 61°C by tuning the polymer structure. When incorporated into applications such as greenhouse materials and thermoelectric devices, significant performance enhancement is observed, due to the thermochromic material functioning as a thermal valve, speeding up solar heat absorbance while inhibiting the cooling process via its phase transition.

Optical responsive asphalt coating with temperature-sensitive TiO2 quantum dots: Formula and temperature adaptability

The application of conventional asphalt contributes to extremely high pavement temperature in hot season as its black color entails large solar absorption. In this study, optical responsive asphalt is proposed to control pavement temperature, which is developed by introducing temperature-sensitive TiO2 quantum dots (TiO2 QDs) into traditional asphalt. Temperature-sensitive TiO2 QDs are prepared by blending thermochromic polymer and TiO2 quantum dots with varied concentrations. Optical characterizations on temperature-sensitive TiO2 QDs have demonstrated that peak value of solar absorption in temperature-sensitive TiO2 QDs at 45 °C is 14.29 %–22.86 % higher than that at 15 °C; the maximum fluorescent intensity of temperature-sensitive TiO2 QDs at 45 °C is 8.5 % higher than that at 15 °C. The results from optical characterizations on temperature-sensitive TiO2 QDs modified asphalt show that the incorporation of temperature-sensitive TiO2 quantum dots endows asphalt low solar reflectance at high temperature and high solar absorption at low temperature. Fluorescent intensity of modified asphalt at 45 °C is increased by 21.6 %, 10.2 % and 5.7 % than that at 15 °C for asphalt containing 5 %, 10 %, and 20 % temperature-sensitive TiO2 QDs, respectively. Indoor solar radiation simulation tests have revealed that compared with traditional asphalt, temperature-sensitive TiO2 QDs modified asphalt coating could yield cooling effectiveness of 6.4 °C at high temperature. Meanwhile, outdoor solar radiation test indicates TiO2 QDs modified asphalt coating could realize warming effectiveness of 0.7 °C at low temperature. The outcomes on temperature-sensitive TiO2 QDs modified asphalt with temperature-adaptability properties makes an advancement in functional pavement.

Thermochromic Polymer Nanocomposites for the Heat Detection System: Recent Progress on Properties, Applications, and Challenges.

Reversible thermochromic polymers have emerged as compelling candidates in recent years, captivating attention for their application in heat detection systems. This comprehensive review navigates through the multifaceted landscape, intricately exploring both the virtues and hurdles inherent in their integration within these systems. Their innate capacity to change colour in response to temperature fluctuations renders reversible thermochromic nanocomposites promising assets for heat detection technologies. However, despite their inherent potential, certain barriers hinder their widespread adoption. Factors such as a restricted colour spectrum, reliance on external triggers, and cost considerations have restrained their pervasive use. For instance, these polymer-based materials exhibit utility in the domain of building insulation, where their colour-changing ability serves as a beacon, flagging areas of heat loss or inadequate insulation, thus alerting building managers and homeowners to potential energy inefficiencies. Nevertheless, the limited range of discernible colours may impede precise temperature differentiation. Additionally, dependency on external stimuli, such as electricity or UV light, can complicate implementation and inflate costs. Realising the full potential of these polymer-based materials in heat detection systems necessitates addressing these challenges head-on. Continuous research endeavours aimed at augmenting colour diversity and diminishing reliance on external stimuli offer promising avenues to enhance their efficacy. Hence, this review aims to delve into the intricate nuances surrounding reversible thermochromic nanocomposites, highlighting their transformative potential in heat detection and sensing. By exploring their mechanisms, properties, and current applications, this manuscript endeavours to shed light on their significance, providing insights crucial for further research and potential applications.

A Stable and Self‐Healing Thermochromic Polymer Coating for All Weather Thermal Regulation

AbstractEnergy‐free thermal regulation is in great demand nowadays. Thermochromic materials are widely explored and used in smart windows. However, most thermochromic materials have fixed transition temperature and still suffer from poor stability. To overcome this challenge, a thermochromic polymer coating based on ion–dipole interaction with switchable transition temperature, high stability toward several harsh environments, self‐healing, and radiative cooling property is developed. It can continuously tune from transparent to opaque according to the temperature change. The lower critical transition temperature can be tuned from 33 to 43 °C by simply adjusting the composition of ionic liquids. Owing to the fluorine polymer backbone and dynamic ion–dipole interactions, it can also keep stable in aquatic, −20 °C, and 70 °C environments and self‐heal upon damage thus prolonging its working life for real applications.

Multi-field driven thermochromic films with phase change energy storage properties

Phase change energy storage microcapsules (PCESM) are commonly used for energy storage and energy conservation management. The device has the function to absorb and store external energy by doping PCESM. In the field of optoelectronic displays, the multi-field driven thermochromic film (TCF) was driven through continuous action of electric field and temperature field to realize the special display function of TCF. The study presents a multi-field driven thermochromic films with phase change energy storage properties (PCES-TCF). PCES-TCF is constructed by thermochromic liquid crystal layer and polymer dispersed liquid crystal layer. In the performance experiments, the effects of diluent, liquid crystal and PCESM contents on the electro-optical properties of PCES-TCF were mainly investigated. In the film formation experiments, PCES-TCF is driven by the electric and temperature fields for transmittance and color change, while preparing multi-color patterns. The film formation on either rigid or flexible substrates possesses stable phase change energy storage as determined by infrared thermography and differential scanning calorimetry (DSC). PCES-TCF has a strong potential for application by reducing external energy consumption based on enhanced color change time controllability.

Corona-Enabled Electrostatic Printing for Ultra-fast Manufacturing of Binder-Free Multifunctional E-Skins.

As essential components in intelligent systems, printed soft electronics (PSEs) are playing crucial roles in public health, national security, and economics. Innovations in printing technologies are required to promote the broad application of high-performance PSEs at a low cost. However, current printing techniques are still facing long-lasting challenges in addressing the conflict between printing speed and performance. To overcome this challenge, we developed a new corona-enabled electrostatic printing (CEP) technique for ultra-fast (milliseconds) roll-to-roll (R2R) manufacturing of binder-free multifunctional e-skins. The printing capability and controllability of CEP were investigated through parametric studies and microstructure observation. The electric field generation, material transfer, and particle amount and size selecting mechanisms were numerically and experimentally studied. CEP-printed graphene e-skins were demonstrated to possess an outstanding strain sensing performance. The binder-free feature of the CEP-assembled networks enables them to provide pressure sensitivity as low as 2.5 Pa and capability to detect acoustic signals of hundreds of hertz in frequency. Furthermore, the CEP technique was utilized to pattern different types of functional materials (e.g., graphene and thermochromic polymers) onto different substrates (e.g., tape and textile). Overall, this study demonstrated that CEP can be a novel contactless and ultra-fast manufacturing platform compatible with the R2R process for fabricating high-performance, scalable, and low-cost soft electronics.

Ultra‐Compliant and Tough Thermochromic Polymer for Self‐Regulated Smart Windows

AbstractSmart windows have shown powerful potential in modulating sunlight and energy management. However, there has not been a single system that can simultaneously possess all desired properties, that is, high compliance, wide tunability, and autonomous regulation. Here, a novel system based on polyhedral oligomeric silsesquioxane crosslinked poloxamer is demonstrated. The as‐synthesized material simultaneously possesses a number of the desired properties for smart windows. In addition, with the incorporation of gold nanorods, the as‐fabricated smart window can be operated in an autonomous fashion with its transmission being modulated automatically upon environmental temperature shifts. Finally, the high toughness and high stretchability (10 000% strain) of the material also pave a way for future applications in wearable displays or flexible window screens.

Reversible Thermochromic Photonic Coatings with a Protective Topcoat.

The fabrication of reversible and robust thermochromic coatings remains challenging. In this work, a temperature-responsive photonic coating with a protective topcoat is fabricated. A cholesteric oligosiloxane liquid crystal possessing a smectic-to-cholesteric phase-transition temperature response is synthesized. A planar alignment of its cholesteric phase is possible with blade coating. By stabilizing with 3 wt % of a crosslinked liquid crystal network, the photonic coating shows a color change ranging from red to blue upon heating. High transparency is retained, and the structural color changes are fully reversible. A transparent polysiloxane layer can be directly applied on top of the cholesteric layer to protect it against damage without affecting its optical properties. This approach satisfies the basic requirements of thermochromic polymer coatings, as it combines easy processability, coating robustness, and a reversible temperature response.

Liquid Thermo-Responsive Smart Window Derived from Hydrogel

Summary Buildings account for 40% of global energy consumption, while windows are the least energy-efficient part of buildings. Conventional smart windows only regulate solar transmission. For the first time, we developed high thermal energy storage thermo-responsive smart window (HTEST smart window) by trapping the hydrogel-derived liquid within glasses. The excellent thermo-responsive optical property (90% of luminous transmittance and 68.1% solar modulation) together with outstanding specific heat capacity of liquid gives the HTEST smart window excellent energy conservation performance. Simulations suggested that HTEST window can cut off 44.6% heating, ventilation, and air-conditioning (HVAC) energy consumption compared with the normal glass in Singapore. In outdoor demonstrations, the HTEST smart window showed promising energy-saving performance in summer daytime. Compared with conventional energy-saving glasses, which need expensive equipment, the thermo-responsive liquid-trapped structure offers a disruptive strategy of easy fabrication, good uniformity, and scalability, together with soundproof functionality that opens an avenue for energy-saving buildings and greenhouses.

A rapid and reversible thermochromic supramolecular polymer hydrogel and its application in protected quick response codes

A rapid and reversible thermochromic fluorescent supramolecular polymer hydrogel prepared by orthogonal self-assembly of host–guest and metal coordination interactions, has been used in protected quick response codes.

A novel photochromic cadmium coordination polymer based on a new viologen ligand accompanying photoswitchable luminescence properties

The self-assembly of a viologen ligand, 1, 1′ -bis((3-carboxylatobenzyl)-4,4′-bipyridinium)-dichloride (H2bcbpy·2Cl), cadmium chloride and terephthalic acid (PTA) has successfully afforded a photo- and thermochromic coordination polymer, [Cd(bcbpy)0.5(PTA)(H2O)] (Cd-BCP), which was characterized by single-crystal X-ray diffraction, powder X-ray diffraction and thermogravimetric analysis. The complex Cd-BCP shows high sensitivity to ultraviolet-visible radiation and heat. Cd-BCP exhibits the rare difunctional properties of both electron-transfer (ET) photochromism and ET thermochromism. Interestingly, Cd-BCP exhibits photocontrolled luminescence properties during the coloration–decoloration process.

Thermochromic Polymer Film Sensors for Detection of Incipient Thermal Damage in Carbon Fiber⁻Epoxy Composites.

Carbon fiber–epoxy composites have become prevalent in the aerospace industry where mechanical properties and light weight are at a premium. The significant non-destructive evaluation challenges of composites require new solutions, especially in detecting early-stage, or incipient, thermal damage. The initial stages of thermal damage are chemical rather than physical, and can cause significant reduction in mechanical properties well before physical damage becomes detectable in ultrasonic testing. Thermochromic fluorescent probe molecules have the potential to sense incipient thermal damage more accurately than traditional inspection methods. We have designed a molecule which transitions from a colorless, non-fluorescent state to a colorful, highly fluorescent state when exposed to temperature–time combinations that can cause damage in composites. Moreover, this molecule can be dispersed in a polymer film and attached to composite parts as a removable sensor. This work presents an evaluation of the sensor performance of this thermochromic film in comparison to ultrasonic C-scan as a method to detect incipient thermal damage in one of the most widely used carbon fiber–epoxy composite systems. Composite samples exposed to varying thermal exposures were used to evaluate the fluorescent thermal sensor films, and the results are compared to the results of ultrasonic imaging and short-beam shear tests for interlaminar shear strength.

Development of a Thermochromic Polymer Insulator

Intelligent materials are those that have the ability to change some physical property in a controlled manner. In the case of the developed insulator, property to be modified is the color. The main objective is that it indicates, by changing its color, when it is in fault condition, thereby facilitating system maintenance because one of the major problem of polymeric insulators is identifying its degradation or failure. After the analysis it was decided that it would be used the thermochromic property. A study of the thermal performance was conducted. Computer simulations and tests on samples were performed. During the modeling has been found the value of heat transfer coefficient of the surface of the insulator (21 W/m2K). After modeling and testing was an insulator made with thermochromic property.

Dual-emission and thermochromic luminescence alkaline earth metal coordination polymers and their blend films with polyvinylidene fluoride for detecting nitrobenzene vapor

A facile and effective approach is proposed for fabricating dual-emission luminescent blend films used as dual signal transducer for nitrobenzene vapor detection with excellent performances.

Design of thermochromic polymer blends containing low‐mass compounds

ABSTRACTWe investigated the light transmittance of an immiscible polymer blend comprising a copolymer of ethylene and vinyl acetate (EVA) and a terpolymer of vinyl butyral, vinyl alcohol, and vinyl acetate (PVB). Both EVA and PVB are used in the interlayers of laminated glass. We found that the transparency of the blend depends on the ambient temperature. This can be attributed to the difference in the temperature dependence of the refractive index between EVA and PVB. The blend has good transparency at room temperature because the difference between the refractive indices of its components is minimal. At high or low temperatures, however, the blend becomes opaque owing to light scattering. The addition of a plasticizer favorably affects the temperature range over which the blend exhibits high transparency, because the refractive index and its temperature dependence are affected by the plasticizer. We also evaluated the interphase transfer of a plasticizer between EVA and PVB at various temperatures. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45927.

Optimization of VO2 nanowire polymer composite thermochromic films by optical simulation

Thermochromic films with high efficiency, transparency, and flexibility are highly desirable for energy-efficient smart window films. Vanadium oxide (VO2)-nanoparticle-embedded flexible polymer composite films are the most promising thermochromic films because of the sharp phase transition of insulating to metallic phases of VO2 at 68 °C with visible transparency and a large change in transmittance at near-infrared wavelengths before and after the metal–insulator phase transition. This paper describes the simulation of high-efficiency thermochromic polymer composite films embedded with VO2 nanoparticles of various sizes to investigate the optimum VO2 nanowire size and length.

Preparation of thermochromic polymer nanocomposite films from polymerizable organogels of oligothiophene-based organogelators

Thermochromic polymer nanocomposite films were prepared from polymerizable organogels. Organogelator 1 had a structure which 3,4,5-tris(ω-decenyl)benzamide groups were attached to a quarterthiophene core through amide bonds. Organogelator 2 had the same structure except that tris(ω-decenyl) groups were replaced by tris(n-decanyl) groups. The PMMA nanocomposite films were prepared by the photopolymerization of the organogels formed in methyl methacrylate (MMA). The film containing 1 (0.5 wt%) showed reversible thermochromism. The emission under 365 nm irradiation was changed to bright green from orange by heating up to 120 °C and returned to its initial orange by cooling. To the contrary, the PMMA composite film prepared from the organogel of 2 (0.5 wt%) did not show a reversible thermochromic property. Organogelator 1 with polymerizable terminal vinyl groups was covalently embedded in the PMMA matrix, but 2 was not. The reversible thermochromism was likely caused by the thermally reversible conformational change of quarterthiophene units in the polymer fibers.